Project report, Ling feng summer research in · Web viewProject report, Summer Research School in Xiamen 2008. By Kalle Koinberg Henrikson [email protected] Response of calcification

Project report, Summer Research School in Xiamen 2008. By Kalle Koinberg Henrikson [email protected]

Response of calcification and photosynthesis to an elevated

pCO2 by calcifying organism Emiliania huxleyi

Spring 2008

Kalle Henrikson Koinberg, [email protected] Research school in Xiamen

Key wordsEmiliania huxleyi, coccolithophorid, oceanic acidification, calcification, elevated pCO2.Abstract


During the past 150 years the CO2-level in the atmosphere has increased because of human activities. This causes ocean acidification. When the pH lowers in the oceans, many organisms will take harm, such as calcifying organism Emiliania huxleyi, EHUX. The target of this research was to investigate how EHUX would react on different pCO2. This was done by measuring [Ca2+], TA, cell density, DIC, DOC, POC and PC when cultivating EHUX in different pH-conditions during a short-term period. Three different containers were measured, with pH corresponding to present day, year 2100 and a non-regulated control volume. The results showed that the rate of cell growth increased with the lower pH, and was at the last day of measurement about 9.8 % higher in the year 2100 group compared with the present day group,. The year 2100 group had a 36.6 % higher growth rate than the control group. The [Ca2+] did not show any clear trend in any of the containers, and the TA did increase in all three cases. The parameters POC/PC and analysis with SEM have not yet been investigated. The only conclusion that can be made at this point in time is that a high pCO2

stimulates cell growth, which increases cell density.

Table of contents


Introduction

Literature review

The elevated pCO2

Oceanic acidification due to increased pCO2

Effects of a lowered pH on ocean carbonate chemistry and Ca2+ saturation state

Emiliania huxleyi – short facts

Other peoples research results

Method

The system

Sampling

Potentiometric titration of calcium

Titration of Total Alkalinity

Measuring cell density

Results and discussion

Cell density

pH and pCO2

Ca2+

Total Alkalinity

DIC

Outlook

References

Introduction


The human activities have had many effects on the world’s climate and ecosystems during the history of mankind. In the past the effects were of a local kind and comprised such influences as e.g. cutting down forest to give way for farmlands and villages. In the present day, our activities have grown to affect the earth on a global basis, e.g. the global warming (IPCC, 2007) and the acidification of the worlds oceans, both originating from the increased CO2 -level due to anthropogenic burning of fossil fuels such as oil and stone coal (Caldeira, 2003). The increased pCO2 (partial carbon dioxide pressure) changes the earth’s entire climate and ecosystems in many ways (IPCC, 2007), but in this literature review the focus is narrowed down to what effects a raised atmospheric pCO2 will have on ocean acidification, calcium saturation state and thus on calcifying organism Emiliania huxleyi’s photosynthesis and calcification.

The coccolithophorid Emiliania huxleyi, EHUX, is a marine key species with a world wide distribution, and belongs to a group of species that are major contributors to photosynthesis. EHUX is also an important species when it comes to regulating the carbon and calcium chemistry of the ocean (Riebesell, 2000).

Because of EHUX’s important role in the ocean, it is of great concern to investigate how it will be affected by a future elevated pCO2. By cultivating EHUX during a short period of time, in three different containers with pH corresponding to different atmospheric pCO2-levels, the effects on EHUX’s photosynthesis and calcification can be estimated.

Literature review

The elevated pCO2

Carbon dioxide, CO2, is a very important atmospheric gas, affecting both the radiative heat balance of the earth and the calcium carbonate (CaCO3) equilibrium of the oceans (Kleypas, 2006). The CO2 level in the atmosphere has raised from pre-industrial values of ~280 ppm (Jacob 1999) to values around 379 ppm in the year 2005 because of anthropogenic activities (IPCC, 2007).

The pCO2 in the atmosphere has increased dramatically the last 150 years (see Figure 1. below) due to anthropogenic burning of fossil, coal based compounds such as oil and stone coal (Caldeira 2003). The many new discoveries and inventions of the humans that emerged during the industrialization craved a lot of energy. Oil and


stone coal were satisfying those energy demands. However, combustion of fossil fuels leads to emissions of CO2 to the atmosphere which have resulted in a steady

Figure 1. The changed pCO2 in the atmosphere from the late 50´s to present day. Picture from “Earth systemresearch laboratory”.(ESRL, 2008)

increase of the pCO2 since the beginning of industrialization.

Oceanic acidification due to increased pCO2

One of the sinks for atmospheric carbon dioxide is the uptake by the oceans. When there is a constant pCO2 over a water surface, CO2(g) gets in a state of equilibrium with CO2(aq) where CO2(g) solves in water to form carbonic acid. See Figure2. and Reaction 1. below (Jacobs, 1999).

Figure 2. CO2(g) – Atmospheric carbon dioxide solves in water to form carbonic acid.


Reaction 1.

Carbonic acid (CO2 · H2O) is a weak diacid that dissociatesin two steps to form HCO3-

(bicarbonate) and CO3 2- (carbonate), the reactions are described by the chemical

equilibriums visualized in Reactions 2. and 3. below. (Jacobs, 1999).

Reaction 2. And reaction 3. 2 is above and 3 is below.

The rates of dissociation in Reaction 2. and Reaction 3. are given by the reactions dissociation constants, and illustrated in Figure 3 below. The TCO2 (total amount of carbon dissolved in water) is also illustrated in Figure 3. The state of the chemical compound is pH dependent.

Figure 3. TCO2 in the ocean. The state of the chemical compound is pH dependent. (Figure 3. Is inspired by Jacobs 1999.)

When the level of carbon dioxide in the atmosphere is raised, the amount of dissolved carbonic acid in the oceans also increases according to Henry’s law (Jacobs, 1999) see equation 1. below.

Equation 1.


Where KH = KH(T) is Henrys constant, a temperature dependent constant that determines how much CO2(aq) that will form in water for a given pCO2.

So when the CO2(g) is increased, the CO2(aq) increases as well, which effects the oceans by lowering the pH.

Models have been made to calculate how the pCO2 will affect the oceans pH (Kleypas, 2006). See Figure 4. below.

Figure 4. Models have been made where the simulated future pCO2’s effect on oceanic pH has been calculated. As the pCO2 increases, the pH decreases in the ocean’s surface water. (Figure yyy. is taken from Kleypas et Al. 2006).

Effects of a lowered pH on ocean carbonate chemistry and Ca2+ saturation state

As the pH in the oceans lowers the [CO32-] will decrease, according to the graphs

(Figure 3. and the carbonate chemistry reaction where CO2(aq) reacts with carbonate and water to form two bicarbonate ions (Orr, 2005). See Reaction 4 below.

Reaction 4.

The decrease in [CO32-] and the lowered pH will disturb the calcium carbonate

(CaCO3 (aq)) balance in the oceans.


In the present day, the surface waters are saturated with calcium carbonate ions, but if the pH continues to decrease as estimated, some parts of the oceans will get under-saturated as soon as within the next 40-50 years (Orr, 2005). This will affect many of the ocean’s key organisms such as some plankton and corals that use calcium carbonate for building up their cell walls (Orr, 2005).

The calcium saturation state, which describes the concentration of Ca2+ in a water volume, is calculated with equation 2. shown below.

Ω=¿¿, 0≤Ω≤1

Equation 2.

When the pH decreases the CO32- decreases as well, and this will lower Ω , the

calcium saturation state. This will decrease the amount of Ca2+ ions in the ocean.

Emiliania huxleyi – short facts

Emiliania huxleyi, also known as EHUX, is a one-celled flagellate that uses lime to build up its’ cell-wall. It is photosynthesizing, hence abundant in the photic zone (SMHI, 2008). Figure 5. below depicts EHUX. The picture is an electron photo, i.e. the plankton is greatly enlarged.

Figure 5. To the left: One specimen of coccolithophorid Emiliania huxleyi. To the right: Two of the CaCO3

- consisting plates that EHUX forms to build up its’ cell wall. Those plates are called coccoliths. The figure is taken from SMHI 2008.

EHUX is an interesting subject of investigation because it:

1. Is a bloom-forming plankton alga with world-wide distribution (Riebesell, 2000). (It exists and blooms for example in waters west of the Scandinavian cost, as shown in figure 6. below.)


2. Belongs to the group of organisms that contribute to the major part of photosynthesis and therefore very important (Riebesell, 2000).

3. Provide the ocean floor with a constant rain of CaCO3 (Riebesell, 2000).

(The coccolithophorids’ turquoise color seen in figure 6. derivates from the reflection of sunrays on their calcium carbonate shell-plates (SMHI, 2008)).

Figure 6. The turquoise-colored algal bloom west of the Norwegian coast is caused by Emiliania huxleyi. The algae are not toxic. (Figure qqq. is taken from SMHI 2008)

Emiliania huxleyi is as mentioned above, an important species for the calcium and carbonate equilibriums in the ocean. While living, EHUX binds in Ca2+(aq) HCO3

-(aq) and CO3

2-(aq) from the water and photosynthesize to grow and breed. When growing, they form their cell-walls with CaCO3 (See reaction 5. and 6. Below).

Ca2+¿+2 HCO3−¿ ⇒CaCO 3+CO 2+H2O ¿ ¿

Ca2+¿+CO32−¿ ⟹CaCO3 ¿¿

Reactions 5. and 6.

As EHUX eventually die, they sink to the bottom of the ocean, contributing to a constant flow of CaCO3 that sediment on the ocean floor. This is very important for regulating the oceanic carbon cycle as well as the CO2 exchange between the ocean and the atmosphere (Riebesell, 2000).

Other peoples research results

To investigate the effects of an increased atmospheric pCO2 on EHUX, experiments have been made where EHUX is bred in water-filled containers with pH


corresponding to different atmospheric CO2 levels. The pH in the tanks is estimated from simulations of a future atmospheric CO2 level. Those experiments often compare the estimated CO2 of year 2100 with the present-day values. Such experiments have been made by e.g. Riebesell et. Al. 2000 and Leonardos & Geider 2005, to name a few.

The results of different investigations show that an increased pH can result in an increased uptake of carbon, and can result in a decreased calcification. The cells cell-walls are more often misshapen, making the algae weak and unfit for survival. A comparison between how EHUX can look like at present day pCO2, and with year 2100 pCO2 is demonstrated in figure 7. below.

Figur 7. To the left: A healthy EHUX. To the right: A EHUX exposed to an atmospheric pCO2 corresponding to the one of year 2100. Its´ cell-wall is greatly deformed, the coccoliths are dissolving. The picture is taken from Riebesell et. Al. 2000.

In an experiment by Leonardos & Geider, 2005 with a non-photosynthesizing strain of EHUX it is shown that carbon dioxide uptake increases with about 15-19% when exposing EHUX to a higher CO2(aq) concentration. This contributes as a negative feedback to the increased pCO2 level, and is therefore a carbon sink. That experiment however was performed under some special conditions, namely high light intensity and low nutrition levels.

In an article by Orr et. Al., 2005 it is written that the Ca2+(aq) under-saturation leads to incomplete cell-walls and deformed EHUX specimen.

Riebesell et.Al., 2000 write that their experiments with a future pCO2 show an increase in CO2-fixation of 8.5 % but that Emiliania huxleyi binds 15.7 % less Ca2+.

Two of the most interesting recent research reports (produced in 2008) are the ones by Jason M. Hall-Spencer et.al and M. Debora Iglesias-Rodriguez et. al.

Jason M. Hall-Spencer et. al have made an in situ study in how an high pCO2 affect a


shallow, coastal ecosystem close to the island of Ischia, Italy. CO2 emitted from underwater vents lowered the pH at the sites of investigation. At sites where the pH was lowered to values about 7.8-7.9, from 8.1-8.2 (which is normal in the area) the amount of coralline algae decreased.

M. Debora Iglesias-Rodriguez et. al. show that EHUX response to higher pCO2 is a higher rate of calcification and also a higher net primary production. Their data show that the coccolith mass has increased with about 40 % the last 220 years.

Method

The system

The system for cultivating EHUX consists of three 5 l glass containers, each from the beginning containing 3.5 l SCSw (South China Sea water), a tube with compressed air containing 1 % carbon dioxide and “IKS Aquastar”, a pH-controlling system, sensors, vaults and CO2 dispensers.

The SCSw has been rid of viruses through high temperature treatment (120。C), and

purified through filtration. Before start of cultivation 30 ml NaNO3, 30 ml NaHPO4, 30 ml of trace metals and 3 ml of vitamins were added to each container to provide as nutrition for the algae. The containers were covered with cotton cloths, attached with rubber bands, to prevent introduction of viruses to the system.

The pH-regulator “IKS Aquastar” was connected after calibrating its’ three pH-sensors. The calibration was made with two different pH-buffers, one with pH 4.00 and the other with pH 7.00.

The pH-control was made by programming “IKS Aquastar’s” to predetermined values. “IKS Aquastar’s” valves were connected to the tube containing CO2, and then connect small dispensers to the valves. The dispensers were then put below the water surface.

The “IKS Aquastar” was programmed to bubble CO2 in the water of container nr. 2 and nr. 3 when pH exceeded 8.00 (nr. 2) respectively 7.80 (nr. 3). Container nr. 1 had no pH control, and was considered an upper pH control volume.

The room of cultivation was 20。C and equipped with lamps that were lit for 14

hours, and turned of for 10 h every 24 h. Those lamps served as an artificial source of sunlight.


The figure 8. below shows the system.

Figure 8. The system for cultivation. The “IKS Aquastar” can be seen to the right, in the middle, the CO2 tube and to the left are the sampling batches with pH-sensors and CO2 dispensers.

Sampling

Before taking samples, the glass containers were thoroughly mixed.

Thin tubes made of silica gel µthat had been washed with distilled water were inserted in the water to enable sampling. The cotton cloths were still on the top of the glass containers. The water was transferred from the containers via the tubes by creation of an under pressure at the outside-end of the pipe. The water was then poured into the different sampling bottles.

Samples were taken daily after the start of cultivation. The first sample was taken the 26/6/2008, and then sampling continued until 4/7/2008. Samples were taken between about 16.00 and 17.15 in the afternoon. See table 1. below for more exact sampling times.

pH, Ca2+(concentration of calcium), TA (total alkalinity), DIC (dissolved inorganic carbon) and the cell density were sampled daily during the period. During the period of exponential growth (30/6/2008 – 2/7/2008), POC (particle organic carbon), PC (particle carbon) and DOC (dissolved organic carbon) were additionally sampled. See table 1. below for more exact sampling information.


Table 1:

Date Container DIC TA Ca2+ Cell-density

pH DOC PC POC

26/61 16:18 16:23 16:27 16:30 16:182 16:38 16:39 16:41 16:43 16:183 16:48 16:50 16:52 16:54 16:18

27/61 16:39 16:42 16:43 16:43 16:302 16:49 16:53 16:54 16:54 16:463 17:00 17:01 17:02 17:02 16:55

28/61 16:28 16:30 16:31 16:31 16:272 16:36 16:37 16:38 16:39 16:353 16:45 16:46 16:47 16:47 16:43

29/61 16:23 16:24 16:25 16:26 16:262 16:29 16:31 16:31 16:32 16:323 16:34 16:36 16:37 16:37 16:39

30/61 16:18 16:21 16:22 16:28 16:24 16:08 16:17 16:112 16:40 16:35 16:37 16:37 16:24 16:29 16:33 16:293 16:51 16:53 16:54 16:54 16:24 16:45 16:49 16:45

1/71 16:16 16:13 16:13 16:14 16:05 16:06 16:08 16:062 16:38 16:34 16:34 16:35 16:05 16:29 16:31 16:293 16:50 16:47 16:48 16:48 16:05 16:42 16:45 16:42

2/71 16:30 16:26 16:27 16:28 16:21 16:22 16:25 16:252 16:41 16:39 16:40 16:40 16:21 16:35 16:36 16:353 16:55 16:52 16:53 16:53 16:21 16:47 16:51 16:48

3/71 16:24 16:15 16:16 16:16 16:142 16:28 16:25 16:27 16:27 16:143 16:35 16:31 16:33 16:33 16:14 SEM

4/71 16:13 16:22 16:23 16:23 16:12 16:252 16:30 16:31 16:32 16:32 16:12 16:323 16:36 16:39 16:39 16:40 16:12 16:40

The following amounts of water were sampled:

Cell density = 2 x 1 mlCa2+ = 10 mlDOC = 30 mlDIC = 40 ml


POC = 50 mlPC = 50 mlTA = 60 ml

All the samples, except for the cell density samples, were saved in a 4。C refrigerator.

Potentiometric titration of calcium

Potentiometric titration of calcium was used for measuring the [Ca2+]. The titration was made with “Metrohm 809 titrando” and “Metrohm 801 stirrer”. Measure pointes were monitored by computer program “Tiamo”.

“Sartorius BS 224 S” scale was used. About 4 g each HgCl2 solution, South China Sea water, and 1 mM EGTA (glycol-bis(2-aminoethylether)-N,N,N',N'-tetra acetic acid) was weighted, and then mixed with about 4 ml of pH=10 buffer solution and 20 ml of distilled water.

Before starting the titration, the gear was checked for stability through titration of 6 samples of HgCl2, 3 samples of “IAPSO” standard water, and 3 samples of “2nd standard water”. The standard deviations divided by the mean values of the concentrations were less than 0.1 %.

The solution was then potentiometrically titrated till the endpoint.

The measure points were input in computer program “Origin” for mathematical calculations of the endpoint. The endpoint and the exact weights of HgCl2, South China Sea water and EGTA were then input in an “Excel” file for calculations of the [Ca2+].

Titration of Total Alkalinity

Titration was used for determination of total alkalinity. The same gear was used as in the titration of Ca2+. About 25 g of SCSw was weighted and titrated with 0.025 M HCl to the endpoint. The measure points were input in “Origin” where the endpoints were found. Those values together with the weights measured with “Sartorius BS 224 S” scale were input in an “Excel” worksheet for calculations of the alkalinity.

Measuring cell density

The cell density was sampled daily according to the procedure described above. 2 x 1 ml of the cultured water was sampled every day, except the first day. That day only one ml was sampled. The water’s cell density was calculated using “Beckman Coulter – Z2 Coulter Particle Count and Size Analyszer”. The machines’ sensor can recognize


cells because of the cell walls’ negatively charged surface.

Results and discussion

Cell density

The cell density in the different containers varied greatly, and increased with time in all of the cases. The cell density per ml is shown in figure 9. below.

1 2 3 4 5 6 7 8 90

100000

200000

300000

400000

500000

600000

700000

800000

900000

Container 2Container 1Day of measurement

Day of measurement

Cells

/ m

l

Figure 9. The cell densities in the different containers increased with time, but at different degrees.

It was unexpected that the cell density was highest in the batch with the highest pCO2. The lower pH was expected to reduce the cell productivity.

Another way to estimate the cell productivity is by calculating the growth rate. The growth rate, μ, between two points in time is defined in equation 3 as:

μ=ln (N n )−ln (N0)

T n−T 0

Equation 3.

where Nn is the number of cells ml-1 the nth day of measuring, N0 is the initial amount of cells ml-1. Tn is day nr. n that has past from T0, and T0 is the initial day.

The growth rates were calculated between the first day of measurement, to the eight


day. The reason is that the last value was discarded is because it decreases on the 9th day in container 1. and 3. so that data set was not considered fully reliable.

When dividing the growth rate in the high pCO2 container with the growth rate in the control volume, the result was a 36.6 % higher growth rate in the one with high pCO2. When comparing the highest pCO2 container with the medium high pCO2, the highest pCO2 had a 9.8 % higher growth rate.

pH and pCO2

The pH from the different containers were measured daily during the sampling period. The result is shown in figure 10. Below. The increase in pH in container 2. and 3. during the fourth day of measurement is because the CO2 was used up. However, a replacement tube was inserted after one day, and then the pH normalized.

1 2 3 4 5 6 7 8 97.2

7.4

7.6

7.8

8

8.2

8.4

8.68.8

9

Container 1Container 2Container 3

Day of measurement

pH

Figure 10. how the pH change with time In the different containers.

There was a steady pH increase in the control volume, container 1. because of the photosynthetic reaction where hydrogen ions are consumed.

Except for the increase in pH on the fourth day of measurement, visualized as a small peak, the pH remained stable during the incubation time.

The pCO2 corresponding to the different pH were calculated with the “Excel” program “CO2sys”, and are displayed in figure 11. below.


1 2 3 4 5 6 7 8 90.0

100.0200.0300.0400.0500.0600.0700.0800.0900.0

1000.0

Control voulmepH 8 volumepH 7.8 volume

Day of measurement

pCO

2

Figure 11. The pCO2 corresponding to the different pH.

The dip on the fouth day, originates from the same reason as the increase of pH mentioned above. There was a steady decrease in the control volume because there is no added CO2 to that volume.

Ca2+

The concentration of Ca2+ varied in the containers. It was highest in the container

with pH=7.8 and lower in the one with pH 8.0. This was expected because of the relation between carbon dioxide and Ca2+:

Ca2+¿+2 HCO3−¿ ⟺CaCO3+CO2+H 2O ¿¿

Reaction 7. Calcification

Since there was a constant inflow of CO2, the equilbrium is forced to the left which causes an increase in calcium ion concentration.

When comparing the [Ca2+] in the container with the highest pCO2 with the other controlled batch, the [Ca2+] is highest in the container with highest pCO2. This is because of the equilibrium in reaction 7. above. So that result was expected.


1 2 3 4 5 6 7 8 99.95

10

10.05

10.1

10.15

10.2

pH 8pH 7.8

Day of measurement

Ca (m

ol/k

g)

Figure 12. The variations in [Ca2+] with time

The fact that the lines are following each other, and have peaks and dips in the same places indicates that some fluctuations in [Ca2+] occurs, maybe on a day/night basis. We cannot explain those fluctuations. This matter would be a good thing to investigate further, by for example sampling measure points more often, perhaps both in the night and the day. With more measurepoints to plot, the fluctuations relation might be more clear.When looking at the [Ca2+], without excluding the control volume, the result is shown in figure 13 below, and is not equally good. The control volume was expected to show an even lower [Ca2+] than the one in the other batches, and should not exceed the value of pH 8-container.

1 2 3 4 5 6 7 8 99.9

9.95

10

10.05

10.1

10.15

10.2

Control volumepH 8pH 7.8

Day of measurement

Ca (u

mol

/kg)

Figure 13. The controlvolume is not excluded.


Total Alkalinity

The total alkalinity is the sum of the negative ions in a water volume minus the positive ions, and indicates the buffering ability.

The alkalinity increased in all three containers. But least in the control volume. The increase was almost equal in the two other batches.

1 2 3 4 5 6 7 8 92000.0

2100.0

2200.0

2300.0

2400.0

2500.0

2600.0

2700.0


Day of measure

Alka

linity

(mol

/kg)

Figure 14. The change of TA in the containers.

DIC – dissolved inorganic carbon

The DIC is the sum of the inorganic carbon species, that are defined in equation 4:

DIC = CO2(aq) + HCO3- + CO3

2-

Equation 4.

The DIC increace in the two controlled batches because of the flow of CO2 that is constantly added to the water volume. In the control container, however, the DIC is decreasing due to the consumption of carbon specis during cell growth.


1 2 3 4 5 6 7 8 90.0

500.0

1000.0

1500.0

2000.0

2500.0

3000.0


Day of measurement

DIC

(um

ol/k

g)

Figure 15. The DIC in the three containers.

Outlook

For future cultivations, a larger water volume would be preferably used. During our experiment, we started with ca. 3.5 l water, but this volume was reduced to less than 2 l at the end of incubation time.

Some of the results and trends might be clearer if the incubation would last a longer time. For example the calcium.

A better mixing of the batches before taking samples, would maybe reduce the deviations in the cell counting.

Samples should be taken more often to be able to investigate the fluctuations in calcium concentration.

Maybe it would be a good idea to have pH control in all the batches, because in this case we have a floating parameter in the control volume that is fixed in the other two cases. This would make it easier to compare the different measure points.

At the time of writing and finishing this report, we have not yet received the result from neither PC nor POC measurements because of some stability problems with the analyzing machine. This data would simplify interpretations of results, and help us draw conclusions.

We have not either gotten the chance to use the SEM – scanning electron microscope. It would be interesting to see if there are any differences in cell size and cell deformation between the different cultivations.


References

Articles

Bernstein et. Al. “Climate change: Synthesis report. Summary for policymakers”, 2007 (IPCC report summary)

Caldeira, K. & Wickett, M.E. et. Al. “Anthropogenic carbon and ocean pH”, Nature, 2003

Jason M. Hall-Spencer et. al. “Volcanic carbon dioxide vents show ecosystem effects of ocean acidification”, Nature, 2008

Kleypas, Joan A. et. Al. “Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers: A Guide for Future Research”, 2006

Leonardos, Niklos & Geider, Richard J. “Elevated atmospheric carbon dioxide increases organic carbon fixation by Emiliania huxleyi (haptophyta), under nutrient-limited high-light conditions”, 2005

M. Debora Iglesias-Rodriguez et. al. “Phytoplankton Calcifikation in a High-CO2 World”, Science, 2008

Orr, James C. et. Al. “Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms”, 2005

Riebesell, Ulf et. Al. “Reduced calcification of marine plankton in response to increased atmospheric CO2”, Nature, 2000

Books

Chang, Raymond “General Chemistry”, 2006

Jacob J. Daniel “Introduction to atmospheric chemistry” 1999

Internet references

Earth system research laboratory, ESRL homepagehttp://www.esrl.noaa.gov/gmd/ccgg/trends/co2_data_mlo.html the 29 Apr. 08Swedish weather institute SMHI’s homepage

http://www.smhi.se/weather/baws_ext/info/2003/Skag_katt_algae_2003.htmthe 29 Apr. 08

Documents

Project report, Ling feng summer research in · Web viewProject report, Summer Research School in Xiamen 2008. By Kalle Koinberg Henrikson [email protected] Response of calcification